Next, we will analyse the eigenfunctions of the Laplacian. The term \(A\)  will be treated as a perturbation, so that the eigenfunctions of \(\Delta \)  are obtained from those of \(\Delta _0\)  by means of (quantum mechanical) perturbation theory that terminates at a finite order. This procedure will be explained in the third subsection. The eigenproblem of \(\Delta _0\)  itself will be reviewed in the first subsection. It reduces to a two-particle Schrödinger problem that, in the case of scalar fields, coincides with the \(BC_2\)  Calogero–Sutherland system, [1]}. For spinning fields, the equation is already non-trivial but its solutions, the spinning bosonic partial waves, have been extensively studied in the literature. Thus, the upshot of the whole construction is to obtain superconformal blocks in a systematic way from well known functions.
